Earlier hatching date rather than chick phenotypic quality enhances first-year survival in the black-headed gull

Our study identifies hatching date as the key determinant of post-fledging survival in the black-headed gull. We suggest that the cumulative negative effects of delayed (suboptimal) hatching and fledging in black-headed gulls may outweigh any benefits of elevated condition and immunocompetence at the natal stage, ultimately compromising post-fledging survival. We propose that our findings may be explained by varying levels of temporal (mis)synchronization between peak food availability and key stages of the annual cycle, particularly the early post-fledging period. The study adds to the understanding of the carry-over effects between the successive stages of the life cycle in wild colonial birds.